1. Field of the Invention
The present invention relates to a paper discharge apparatus for a recording system for use in combination with a recording system such as an electrophotographic copying machine.
2. Description of the Prior Art
In recent years, an electrophotographic copying machine has been widely used. In many copying machines, a paper discharge apparatus for externally receiving a copied sheet is arranged as a part of a copying machine main body. In a large or high-speed copying machine, however, an independent paper discharge apparatus 30 is connected to a copying machine main body 20, as shown in FIG. 1. The paper discharge apparatus 30 of this type has a main tray 33 at a top position and a plurality of bins 32 below the main tray 33. The paper discharge apparatus 30 also includes a bin driver 31 for driving the main tray 33 and the bins 32.
The bin driver 31 has a bin ascent/descent control means 35 for moving the main tray 33 and the bins 32 upward/downward. Reference numeral 36 denotes a motor for applying a driving force to the control means 35.
A guide plate 39 for a copying sheet 1 (indicated by an alternate long and short dashed line in FIG. 1) and paper discharge rollers 41 located between the guide plate 39 and the main tray 33 are arranged at substantially the central portion of the driver 31. By driving the paper discharge rollers 41, the copying sheet 1 is discharged into the main tray 33 or a bin 32.
In the paper discharge apparatus 30 of this type, by moving the main tray 33 and the bins 32 upward or downward, a copying sheet is discharged in a corresponding bin. Since an ascent/descent state of the bins is controlled in accordance with the number of sets of copies, copied sheets 1 are discharged in the respective bins as shown in, e.g., FIG. 2A. In FIG. 2A, the number of bins is four. In this case, leading edges la of the copying sheets 1 received in the bins are always aligned as shown in FIG. 2A.
For this reason, when the copying sheets 1 are removed from a plurality of bins, all of the copying sheets removed from all the bins overlap each other as shown in FIG. 2B.
Therefore, when copying sheets are simultaneously removed, for example, they must be sorted in units of bins, resulting in very cumbersome work.
In order to solve this problem, as shown in FIG. 2C, leading or side edges of copying sheets discharged into bins may be offset alternately in odd- and even-numbered bins. For this purpose, a paper discharge apparatus for shifting discharged copying sheets right and left (i.e., in the widthwise direction of a sheet) is proposed in Japanese Patent Publication No. 63-27253. In this paper discharge apparatus, a paper discharge tray is oscillated in order to shift copying sheets right and left.
When copying of a number of sets of copies exceeding the number of bins is performed by using such a shift type paper discharge apparatus, copying sheets are alternately shifted and stacked one after another, thereby increasing a resistance caused by static electricity or friction between the copying sheets. Therefore, especially in the case of copying of a large number of copying sheets, the sorted copying sheets are easily misaligned when they are removed from the bins. In this case, since sorting is disturbed, the copying sheets require realignment.
The paper discharge apparatus 30 as shown in FIG. 1 has two types of paper discharge modes, i.e., sort and non-sort modes. In the non-sort mode, the copying sheets 1 are discharged in only the main tray 33. In the sort mode, the main tray is used as a bin, and a set number of copying sheets 1 are sorted and discharged in the main tray 33 and the remaining bins 32. Therefore, when the last bin is used, the bin ascent/descent control means 35 drives and moves the bins 32 upward as shown in FIG. 3.
In the paper discharge apparatus 30 having the above arrangement, the copying sheets 1 are received in only the main tray 33 when the non-sort mode is selected. The number of copies which can be received in the main tray 33 is normally about 150 to 200. Therefore, in order to copy a number of sheets larger than this number in the non-sort mode, the maximum receivable number of sheets of the main tray 33 is set. After the receivable number of copies are received , the copying sheets are removed of the main tray 33, and the number of remaining copies is set to perform copying. This operation and work are very cumbersome.
When a user sets the number of copies larger than the receivable number of the main tray 33, copying sheets sometimes overflow from the main tray 33 to the outside, thereby causing jamming.